rxrpc: Fix local destruction being repeated

rxrpc: Fix local destruction being repeated

[ Upstream commit 01dbde5f1a70143844a9b714511736fe329b9ada ]

If the local processor work item for the rxrpc local endpoint gets requeued
by an event (such as an incoming packet) between it getting scheduled for
destruction and the UDP socket being closed, the rxrpc_local_destroyer()
function can get run twice.  The second time it can hang because it can end
up waiting for cleanup events that will never happen.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>